1. Field of the Invention
The present invention relates generally to hearing protection earplugs comprising a shell for being worn at least in part in the ear canal of a user and a faceplate at the outer end of the shell or within a cavity of the shell having an outer opening, and is specifically directed to such hearing protection earplugs which allow for in-situ measurements within the shell and/or the ear canal. The invention is further relates a corresponding manufacturing method and to a use of such earplugs.
2. Description of Related Art
A large part of the population is exposed to hazardous noise from time to time. This can be at work, whilst traveling, during leisure activities or at home. The exposure can lead to permanent hearing loss, distract people's attention from other hazards or simply cause stress. In order to prevent both accidents and permanent hearing damage, hearing protection devices (HPDs) have been provided in many styles and over many years. It started with the earmuff which is still very relevant and addresses very noisy environments (e.g. airports, construction, shooting) or complex working/communication situations (e.g. fighter pilots). Over the years development of biocompatible soft materials has enabled soft earplugs in different styles and colors as well as recent development of “one fits many” standard semi-soft earplugs in silicon-rubber type materials. For severe situations even the combination of an earmuff and an “in-the-ear” HPD is required to achieve desired attenuation. The physical limitation of hearing protection based on ear worn devices is defined where bone-conduction (body acoustics) becomes dominant at around 40 dB attenuation.
A common disadvantage of the above mentioned HPD styles is wearing discomfort. In case of the earmuffs, they are large which creates difficulties in combination with other head worn gear and they “close off” the ear too much for most applications. The in-the-ear styles mentioned are devices made to fit “the average” ear in one way or the other. Either the fit is provided by softness of the material which leads to undefined device insertion and undefined attenuation, or the fit is provided by standard shaped structures intended to block off the ear canal. In both cases the flat distribution of the individual shape of the outer ear and the ear canal leads to bad fit, pressure points in the ear and undefined positioning of the device.
To address this wearing comfort issue, in-the-ear hearing aid technology has been applied making customized ear molds with passive acoustical filter. These are long lasting devices with good wearing comfort. However, this customization process is traditionally a very manual process creating varying results over time, low reproducibility and the quality is very operator skill dependent.
The basic idea to use rapid prototyping technology, such as layer-by-layer laser sintering of a powder material, in manufacturing customized shells, primarily for hearing aids, is described, for example, in U.S. Pat. No. 6,533,062 B1 or US 2003/0133583 A1. This technique is successfully being used in hearing aids and can be applied in a similar fashion for HPDs. By doing this, a whole new range of features and functions become feasible for HPDs.
Passive hearing protection devices (HPDs) exist in several forms. They range from a simple earplug made of synthetic foam to fully customized ear moulds with adjustable valves or adjustable attenuation, and from miniaturized invisible ear canal devices to large ear muffs.
Environmental sounds are typically comprised of a mixture of various sound wave frequencies having varying intensities. It is well documented that repeated or prolonged exposure to sounds of sufficiently high sound pressure level can cause temporary or permanent hearing impairment, i.e. can damage the auditory organ and cause serious hearing problems, including deafness. Harmful noise such as caused by explosions or bursts are often comprised of a mixture of sound wave frequencies of varying intensity. These disturbing frequencies are in both the high and low frequency bands and have sufficient intensity to cause hearing problems. Individuals who are frequently exposed to such disturbing and sometimes dangerous noise run the risk of incurring such injuries as hearing loss or even deafness. Such individuals include workers at demolition or construction sites, operators of heavy, noisy equipment and those in active military service. Ear (i.e. hearing) protection is needed to prevent a loss in hearing acuity and the gradual increase in the threshold of hearing resulting from extended exposures to loud noise.
Customized hearing protection devices, i.e. devices individually adapted to the user's ear, are higher priced devices compared to competing soft earplugs. Some of the higher value of such customized devices is defined in better anatomical fit of the device in the ear resulting in enhanced wearing comfort, but also a significant value add is linked to the better control of attenuation.
Usually, the desired sound or noise attenuation is defined by selection of an appropriate sound attenuation filter and, after the assembly of the device, the actually achieved attenuation is measured in-situ for confirmation. Hence customized HPDs mostly have a tube with the filter inserted in it for defined attenuation, and adjacent to this filter tube, a tube for the in-situ measurement of the actually obtained attenuation. This measurement tube should be closed for normal operation of the HPD.
It is usual to provide a pair of HPDs tethered together by means of a cord. Such a tethered earplug device will serve to prevent accidental dropping or loss thereof, be it the two or only one earplug of the pair. This is of importance, for instance, where the HPDs are to be used in an industrial food processing environment or in an environment where a dropped earplug would be likely to become so dirty that it is rendered unusable or lost altogether. In order to allow the fastening of such a security cord, the HPD must be equipped with a cord fastening means.
US 2003/0112990 A1 relates to a hearing protection earplug according to the preamble of claim 1, consisting of a core element surrounded by sleeve which is filled with a curable rubber-like material having a hardness value of less than shore A 30 for individually adapting the earplug to the shape of the user's ear canal and outer ear. The core element comprises a first sound bore which extends through the earplug and which may be detachably connected at its proximal end with a remote measurement apparatus and a second sound bore which is parallel to the first sound bore and which may be closed by an attenuation element or may serve for sound input by a hearing aid unit. The proximal end of the first sound bore is closed by a slit membrane when the first sound bore is not connected with the remote measurement apparatus.
It is an object of the present invention to provide for a hearing protection earplug enabling in-situ acoustic measurements and providing for at least one additional function, while having a compact design. It is a further object to provide for a corresponding manufacturing method and a use of such an earplug.